JPS606045B2 - Method for manufacturing crosslinked polyolefin electric wire - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for producing a crosslinked polyolefin electric wire using a hydrolyzable unsaturated silane.

Conventionally, this type of cross-linked polyolefin electric wire has been produced by reacting a hydrolyzable unsaturated silane and a free radical generator with polyethylene to produce silane-grafted polyethylene, which is pelletized, and then processed using the silane-grafted polyethylene. A polyethylene beret and a separately produced polyethylene beret containing a silanol condensation catalyst are kneaded together, and then the mixed wire is extruded from an extruder to be coated on the conductor, and then brought into contact with moisture to cause crosslinking. It is manufactured by the following method. However, in this method, the silane-grafted polyethylene pellets and the polyethylene pellets containing the silanol condensation catalyst are produced separately, and then kneaded and extruded to produce the crosslinked polyethylene electric wire, so the process is complicated. However, there were disadvantages such as poor productivity and increased manufacturing costs. Therefore, recently, polyethylene berets, unsaturated silane, free radical generator, silanol condensation catalyst, etc. were mixed, this mixture was fed into an extruder from a hopper, and then melted and kneaded. A method for manufacturing a crosslinked polyethylene electric wire has been proposed in which the conductor is coated by extrusion and then crosslinked by contacting with moisture (hereinafter referred to as method A).

In addition, while polyethylene berets, etc. are fed into the extruder from the hopper, the mixed liquid of unsaturated silane and free radical generator and the silanol condensation catalyst are fed through the liquid injection hole provided in the screw or cylinder at separate locations or at the same location. A method for manufacturing a cross-linked polyethylene electric wire, which comprises press-fitting the wire into an extruder using an iron press, melt-kneading it in the extruder, extruding the tsuru mixture from the extruder to coat the conductor, and then contacting it with moisture to cross-link it. A method has also been proposed (hereinafter referred to as method B). Furthermore, polyethylene pellets, unsaturated silane, and a free radical generator are fed into the extruder from a hopper, while a silanol condensation catalyst is introduced into the extruder from a liquid injection hole provided in the screw or cylinder. A method for manufacturing a crosslinked polyethylene electric wire in the same manner as method C has also been proposed (hereinafter referred to as method C). However, in the case of method A, in which the mixture of the silanol condensation catalyst and unsaturated silane is fed from the hopper into the extruder together with the polyethylene beret, the unsaturated silane comes into contact with the moisture present in the atmosphere. The unsaturated silane is hydrolyzed and condensed or polymerized to solidify, and the amount of unsaturated silane required for the reaction not only decreases or changes by the amount of solidified unsaturated silane, but also
The solidified silane may adhere to the bottom of the hopper, making it impossible to constantly supply compounding agents such as polyethylene into the extruder.Also, lumps of solidified silane may adhere to the outside of the polyethylene insulator. .

Also, in the case of method B, in which a mixture of a silanol condensation catalyst and unsaturated silane is pressurized into the extruder through the liquid injection hole, the unsaturated silane solidifies when it comes into contact with moisture, and this solidified silane causes the injection metering pump to close the valve. This causes inconveniences such as clogging of the piping system, making it impossible to pressurize the mixture of the silanol condensation catalyst and unsaturated silane. On the other hand, in the case of methods B and C in which a mixture of unsaturated silane and free radical generator is supplied through the same inlet, when the mixture comes into contact with a heated cylinder or screw, the free radical generator is decomposed. The decomposed free radical generator causes the unsaturated silane to condense or polymerize and solidify.

When the unsaturated silane solidifies in this way, the amount of unsaturated silane required for the reaction decreases or changes by the amount of solidified silane, as in the case of method A above, and it also causes damage to the inside of the cylinder and the screw. This may cause adhesion, resulting in fluctuations in the extrusion rate, and the adhering solidified silane may peel off and adhere to the outside of the polyethylene insulator. The present inventors conducted chain research to eliminate the drawbacks of the conventional methods described above, and as a result, the present inventors discovered that unsaturated silane was By feeding the mixture of silane, silanol condensation catalyst, and free radical generator into the extruder through separate inlets, the disadvantages associated with the above conventional method are eliminated, and good crosslinked polyolefin electric wires can be reliably produced. We saw what we could do, did what we could, and arrived at the present invention.

The present invention will be explained in detail below.

First, one of a mixed solution of a silanol condensation catalyst and a free radical generator and a hydrolyzable unsaturated silane is fed from a hobber into a screw presser together with a polyolefin, and the other is fed into a cylinder or screw. The liquid is injected into the extruder through the provided liquid injection hole.

That is, in one method, a mixed solution of a silanol condensation catalyst and a free radical generator is fed together with a polyolefin from a hopper into a screw extruder, and a hydrolyzable unsaturated silane is fed into a screw extruder from a melting region of the polyolefin moat material. It is press-fitted into the extruder through the liquid injection hole provided at the position. In another method, a hydrolyzable unsaturated silane and a polyolefin are fed into a screw extruder from a hopper, and a mixed solution of a silanol condensation catalyst and a free radical generator is placed at a position after the melting of the polyolefin kneaded product. The liquid is press-fitted into the extruder through the liquid injection hole provided in the extruder. Note that after pre-mixing the mixed solution of the silanol condensation catalyst and free radical generator or the hydrolyzable unsaturated silane with the polyolefin,
Alternatively, the components may be supplied into the extruder from a hopper without being mixed in advance and kneaded in the extruder.

As the above polyolefin, polyethylene ~ polyp. Homopolymers such as pyrene, blends thereof, ethylene-propylene copolymers, and copolymers such as ethylene-butylene copolymers are used.As silanol condensation catalysts, dibutyltin dilaurylate, acetic acid stannous "dibutyltin diacetate""dibutyltinoctoate" lead naphthenate, zinc caprylate "cobalt naphthenate tetrabutyl titanate, tetranonyl titanate" lead stearate "zinc stearate"
Organometallic compounds such as cadmium stearate, barium stearate, calcium stearate are used. This usage amount is 0 parts by weight of polyolefin 10.
．． The range is from 0.05 to 0.5 parts by weight. If it is less than this, the degree of crosslinking will be low, and if it is more than this, the surface texture will become rough. Furthermore, ``Free radical generators include, for example, penzoyl peroxide,
Dichlorobenzoyl peroxide "dicumyl/guoxide" di-t-butyl peroxide, 2,5-di(peroxybenzoate) hexyne-3,1,3-bis(t-
butylperoxyisopropyl)benzene, lauroyl/f-oxide, t-butylperacetate, 2,5
-Dimethyl-2,5-di(t-butylperoxy)hexane-3,2,5-dimethyl-2,5-di(t-butylperoxy)hexane, organic peroxides such as t-butylperbenzoate Which azo compound is used, such as ester or perester, or azobisisobutyronitrile, dimethyl azodiisobutyrate. The amount used is in the range of 0.0002 to 0.002 mol per 10 female polyolefins. When the amount is less than 0.0002 mol, a sufficient degree of crosslinking cannot be obtained, and when it is more than 0.002 mol, molding becomes difficult.

Furthermore, unsaturated silanes that can be hydrolyzed include the following formula RR'SiY2 (where R is, for example, vinyl, allyl, butenyl, cyclohexenyl, cyclobentadienyl, cyclohexadienyl, CQ=C(CH3)COO( CH2)31?C5=C(CH3)COOCH2CH20(CH2)3
−,CH2=C(CH3)COOCH2CH2CH(O
H) C ratio ○ Monovalent olefinic unsaturated hydrocarbon group or hydrocarboxyl group such as (CH2)3-, Y is an alkoxy group such as methoxy, ethoxy, butoxy group, formyloxy, acetoxy group, etc. acyloxy group or propionoxy group, 1ON=C(CH3)
2, one ON = C (CH3) C2 day 5, one ON = C (C6
&) A hydrolyzable organic group such as an oximo group such as 2, an alkylamino group such as 1NHC2, an arylamino group such as 1NH(C65), R is for example methyl, ethyl, propyl , tetradecyl, octadecyl,
A monovalent hydrocarbon group other than an aliphatic unsaturated hydrocarbon group such as phenyl, benzyl, tolyl group, or the same compound as Y) is used.

The amount used is 1 per 100 parts by weight of polyolefin.
~10 parts by weight. If the amount of unsaturated silane used is less than 1 part by weight, sufficient grafting will not occur, while if it is more than 1 part by weight, molding will become difficult. Next~
After the polyolefin and other compounding ingredients supplied from the hopper into the extruder are transferred by a screw and thoroughly melted and kneaded with the polyolefin, the compounding ingredients press-fitted from the liquid injection hole by a metering pump are transferred by the screw while the above Melt and knead with polyolefin kneaded material. Thus, the unsaturated silane and the silanol condensation catalyst are fed into the extruder from separate ports, and after either one is sufficiently mixed with the polyolefin, the other is mixed. Therefore, the unsaturated silane and the silanol condensation catalyst are not directly mixed as liquids, but one of them is diluted with polyolefin, which is considered a type of solvent, so the solidification of the unsaturated silane does not occur, which is the case with conventional methods. The inconvenience of doing so will not occur. Further, the unsaturated silane and the free radical generator are also fed into the extruder from separate inlets, and after either one is thoroughly mixed with the polyolefin, the other is mixed. Therefore, since either one is diluted with the polyolefin, which is considered to be a type of solvent, the unsaturated silane is not solidified by the free radical generator, and the disadvantages associated with conventional methods do not occur. When the free radical generator is fed into the extruder from the hopper, or when it is introduced into the extruder through the liquid injection hole, the temperature of the kneaded material must be controlled to keep the free radicals at bay until the free radical generator is sufficiently mixed with the polyolefin. It is preferable to keep the temperature below the decomposition temperature of the free radical generator; if it is higher than the decomposition temperature of the free radical generator, local crosslinking may occur within the polyolefin, making extrusion difficult.

Next, all the ingredients are thoroughly kneaded at a temperature higher than the decomposition temperature of the free radical generator, and then extruded from an extruder to coat the extrudate on the conductor.

Grafting of the unsaturated silane to the polyolefin occurs in preference to crosslinking of the polyolefin, so extrusion is possible without any disadvantages. Next, the wire is brought into contact with water and crosslinked to produce a crosslinked polyolefin electric wire. As explained above, in the present invention, the hydrolyzable unsaturated silane is not supplied into the extruder from the same inlet as the silanol condensation catalyst and the free radical generator, and the silanol condensation catalyst and the free radical generator are Either the mixed liquid or the hydrolyzable unsaturated silane is fed into the screw extruder from a hopper together with the polyolefin, and the other is pressurized into the extruder from a liquid injection hole provided in the cylinder or screw. ing.

Therefore, there are no problems such as solidification of the unsaturated silane or local crosslinking of the polyolefin, and the crosslinking step and extrusion step can be carried out reliably. Therefore, a polyolefin insulator is reliably formed on the conductor, and this is crosslinked by moisture to produce a high quality crosslinked polyolefin electric wire. Hereinafter, the present invention will be concretely established by showing examples. [Example 1] L/D=28 D=5 The heating zone of the cylinder is divided into five parts, a liquid injection hole is provided between the second heating zone and the third heating zone, and A screw extruder equipped with a wire coating crosshead was used, and the extruder temperature was set as follows.

Cylinder 1st heating zone 130 o Cylinder 2nd heating zone 130q0 Cylinder 3rd heating zone 130q○ Cylinder 4th heating zone 200q○ Cylinder 5th force o Tropical 200q○ Cross head flange 200q○ Cross head 20000 Dice holder 2000
0 A mixture of polyethylene and pinyltrimethoxysilane is introduced from the hopper of this extruder, while a mixture of dibutyltin dilaurate and dicumyl peroxide is injected through the liquid injection hole using a metering pump, and then melted while being transferred with a screw. Kneaded.

Finally, vinyltrimethoxysilane is 2 parts by weight, diptyltin dilaurate is 0.05 parts by weight, and dicumyl peroxide is 0.05 parts by weight, based on the weight part of the polyethylene insulator 10 extruded with each compounding agent. I was encouraged to join the club. Melt kneading was carried out for about 8 hours and extrusion was performed to coat the extrudate onto the conductor. There was no deformation of the crosslinked polyethylene electric wire obtained, and no lumps were attached to the outside of the polyethylene insulator. Furthermore, when the extruder was inspected after the experiment, no solidified silane was found on the screw or cylinder. The properties of the obtained wire are shown in Table 1 below. Table 1 As is clear from the data listed in Table 1 above, a sufficiently crosslinked, high quality crosslinked polyethylene electric wire was obtained.

[Example 2] The same extruder as in Example 1 was used and extrusion was carried out under the same melt extrusion conditions.

However, while a mixture of polyethylene t-dibutyltin dilaurate and dicumyl peroxide was charged from the hopper, unsaturated silane was pressurized from the liquid injection hole. There was no change in the outer diameter of the obtained crosslinked polyethylene electric wire, no lumps were attached, and no solidified silane was attached to the screw or cylinder. The characteristics of the obtained electric wire are as shown in Example 1.
The characteristics were similar to those of the electric wire obtained in . [Comparative example] The same extruder as that used in Example 1 was used except that there was no liquid injection hole, and the same extruder settings were used as in Example 1. Polyethylene, dibutyltin dilaurate, dicumyl/gu oxide A mixture of vinyltrimethoxysilane was charged from a hopper and melted and mixed for about 8 hours, extruded, and the extrudate was coated on a conductor and brought into contact with moisture to produce a crosslinked polyethylene electric wire.

The obtained crosslinked polyethylene electric wire had a variation in outer diameter and had lumps attached to it. Furthermore, ``After the experiment, we inspected the extruder and found that solidified silane had adhered to the screw troughs and inside the cylinder.Table 2 shows the characteristics of the obtained electric wire.From the results in Table 2 and above, we found that It can be seen that the method of the invention (Examples 1 and 2) allows extrusion coating to be performed without any problem and the obtained electric wire has better characteristics than the conventional method (comparative example).

Claims (1)

[Claims] 1 One of the mixed liquid of the silanol condensation catalyst and the free radical generator and the hydrolyzable unsaturated silane is fed into the screw extruder from the hopper together with the polyolefin, and the other is installed in the cylinder or screw. A method for producing a crosslinked polyolefin electric wire, which is characterized by press-fitting a liquid into an extruder through a liquid injection hole, kneading it, extruding it, coating the extrudate on a conductor, and then contacting it with moisture to crosslink it.